This invention relates to a mineral fiberboard, and, more particularly, a mineral fiber acoustical board or unit. 2. Description of the Prior Art
Mineral fiberboards (e.g., acoustical panels) are of commercial value, compared to vegetable fiberboards, because of the incombustibility of the mineral fiber. The acoustical panels are conventionally made with mineral wool fibers and a starch binder. It is customary to impart a desired acoustical rating to these panels by mechanically punching or fissuring them. While, in many conventional ceiling products, the board perforations are necessary for sound absorption and are sometimes decorative, there are certain instances where the perforations detract from the appearance. In these instances, it would be desirable to utilize a ceiling panel which is not perforated but still has high sound-absorption properties.